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    Minus index corr better than plus
    From: Paul Hirose
    Date: 2000 Jul 26, 05:01 EDT

    One reason I prefer a negative index correction is the same one some
    of you stated: it's easiest to read index error when it's on the arc.
    But I will say that reading a few minutes off the arc is not hard.
    Just visualize the 59' mark on the drum as -1', 58' as -2', etc.
    Fractional minutes can be estimated by eye, or you can visualize the
    vernier numbered in reverse as well.
    The other reason I like a negative IC is that it's the same sign as
    the dip correction, so there's less chance of a blunder. At least
    that's the case with star shots, since the refraction correction will
    also be negative. Shooting the Sun's upper limb will give all negative
    corrections too. With the Moon you're going to have both + and -
    corrections regardless of index correction sign, unless the shot is
    quite high-angle.

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